Peter's stomach started churning. He had thought about it, and he couldn't see any reason why he would do something so heinous. Except for one reason, the one stray thought that had crossed his mind a time or two since they left Hogwarts. The one that, if given the chance to germinate and be nurtured by people who had wickedness on their minds and a desire to infiltrate Dumbledore's group.
What if he, Peter, believed in the future that in a way he, himself, had been betrayed? He could hardly stand the thought, but there had been numerous times when he'd felt left out, or the butt of a joke, or the odd one out, over the years. In the year since they left school he'd noticed that while they all tried to get together as often as they could, so many times it seemed that the other three had left him behind.
What if, Peter now considered, his doubts and his fears had been like coals to the Death Eaters, and they had fanned the flamed and convinced him that his friends no longer needed him. That he'd already been betrayed and let down. Yes, then he could see himself returning the favour to his friends, of betrayal and heartache. And death, it would also seem.
Paling, Peter nodded. "I have an idea of why I would." He paused, taking a breath past the boulder that seemed to be sitting on his chest. "What if I thought I'd ready been tossed aside by my best friends, James? If I thought that the only people to have ever really accepted me had rejected me for no reason that I knew of, then yeah, I'd be angry. I'd probably want to get revenge."
He stopped, pulling in another ragged breath. "And if I'd fallen in with Death Eaters, with the Dark Lord and was told only lies, then yeah, I'd make some terrible decisions. I'd know what I was doing, just as I would think that you lot knew what you were doing."
Peter looked down, unable to look James in the face. He'd just revealed to his now former best friend his deepest fear, and not only had it already come true, he was certain that any hope of saving any semblance of friendship was now gone.